1. Field of the Invention
The present general inventive concept relates to a built off testing apparatus, and more particularly, to a built off testing apparatus coupled between a semiconductor device and an external testing apparatus to test the semiconductor device.
2. Description of the Related Art
Generally, after being fabricated, semiconductor devices are functionally tested to evaluate electrical characteristics of the semiconductor device. For example, dynamic random access memory (DRAM) undergoes tests to detect defects in internal memory cells or to evaluate DC characteristic of the DRAM.
FIG. 1 is a block diagram of a conventional external testing apparatus 10.
Referring to FIG. 1, the external testing apparatus 10 may be coupled to a device under test (DUT) 20 by contacting probes (not illustrated) electrically connected to the external testing apparatus 10 via connection cables, to the DUT 20. Then, the DUT 20 may be tested by a predetermined testing program stored in the external testing apparatus 10. For example, in cases where the DUT 20 is a DRAM, the external testing apparatus 10 transmits test information to emulate a writing operation synchronized with the operating frequency of the DRAM to the DRAM, and performs a reading operation to read out information stored in the DRAM in synchronization with the operating frequency of the DRAM. Next, the external testing apparatus 10 determines whether the DRAM is failed or not by comparing an expected value and information obtained from the reading operation.
However, in general, since precision of the waveform and speed of a test signal generated by the conventional external testing apparatus 10 are low relative to the operation frequency of the state of the art semiconductor devices operating at high speed and having high capacity, it is difficult to perform a reliable test with respect to the semiconductor devices. Due to recent increases in operation speed and capacities of these semiconductor devices, conventional external testing apparatuses are becoming outdated or unusable.
Since an external testing apparatus is a relatively expensive apparatus, it is economically beneficial to make use of an existing testing apparatus to test high performance semiconductor devices. As a technique to test high performance semiconductor devices by using a conventional external testing apparatus operating at a relative low speed, a technique to install a built in self test (BIST) circuit in semiconductor devices has been researched. However, the BIST circuit has a challenge to be applied to the semiconductor devices, since the BIST circuit increases the size of the semiconductor devices, and the additional process for fabricating the BIST circuit incurs increase in production costs of the semiconductor device.